Power supplies and power converters are used in a variety of electronic systems. Electrical power is generally transmitted over long distances as an alternating current (AC) signal. The AC signal is divided and metered as desired for each business or home location, and is often converted to direct current (DC) for use with individual electronic devices or components. In an AC power distribution system, the “power factor” refers to the ratio of real power flowing to a node and apparent power in the circuit (the power factor provides an indication of energy transfer efficiency). As desired, power factor correction (PFC) circuits are used in AC power distribution system to improve energy transfer efficiency. Passive PFC circuits use a filter to pass current at a desired frequency or frequency range to improve the power factor. Meanwhile, active PFC circuits change the waveform of current drawn by a load to improve the power factor.
In active PFC circuits, switches are employed. The operations of such switches consume power and affect the efficiency of the PFC circuit. As switching frequencies increase, the importance of managing hard versus soft switching increases due to hard switching having higher losses compared to soft switching. Unfortunately, analyzing switching conditions is not a trivial task.